Doors of the kind that swing in either direction from a closed position are well known in the art. Various closing devices may be used with such doors, for example a cam bearing of the type disclosed in U.S. Pat. No. 3,384,996. In the aforesaid cam bearing of the cam follower, usually in the form of a roller, follows a curved cam track that is elevated on both sides of a central low point which coincides with the closed position of the door. The track is normally mounted on the door jamb, i.e. the vertical member of the door frame about which the door is arranged to swing. When the door is swung to either side of the closed position, the roller rides up on the track. Since the roller is connected to the door through an intermediate structure, it lifts the door vertically by a corresponding amount relative to the jamb. When the door is released, the roller returns to the low point on the track and returns the door to its closed position. In the process the door is lowered to its previous level.
The cam bearing mechanism is normally mounted on the door jamb near the lintel piece, i.e., near the horizontal member of the door frame. A cut-out section of the door, which may have a substantially rectangular configuration, provides the necessary clearance to accommodate the mechanism as the door swings between its open and closed positions. If the door is to act as an effective barrier between the two spaces separated by it, e.g., to seal out kitchen odors from a dining area, the transfer of air between the two spaces must be effectively restrained when the door is in its closed position. Since the door closing mechanism blocks air transfer through the aforesaid cut-out section only partially, a seal is required that will effectively block the passage of air through this space when the door is closed.
In prior art devices of the type disclosed in the aforesaid U.S. Pat. No. 3,384,996, a flexible sealing flap is used for the purpose. Typically, the flap is of a size sufficient to cover the rectangular cut-out section and is mounted on the door jamb so as to resiliently bear against the swinging door. A minimum degree of stiffness is required in order to provide an effective seal. Such stiffness, however, increases the resistance which must be overcome in order to swing the door out of its closed position. Reducing the stiffness of the flap also reduces its effectiveness as a seal. The sealing function is further impaired when, due to repeated motion of the swinging door, the flap loses its flexibility and acquires a set that permits the air to pass through the cut-out.
The problem is further compounded by the fact that the door closing mechanism, particularly for heavy doors, is frequently of a size where it extends beyond the thickness dimension of the door. Where that is the case, the use of a substantially planar, flexible flap no longer presents a feasible solution, due largely to interference by the protruding mechanism and to the relative dimensions of the other components of the door structure.